1. Abdominal Wall/Peritoneum and Mesenteries

Superficial fascia

Loose connective tissue with varying levels of adipose tissue

Types of superficial fascia

- Camper's fascia

- Scarpa's fascia

Camper's fascia

- Loose

- Most of adipose tissue on entire abdomen well

Scarpa's fascia

- Deepest layer of superficial fascia (very thin, keeps fat from muscle)

- Higher elastic tissue

- Low adipose (same on everyone)

Deep fascia (+ function)

- Encases muscles

- Allows independent movement

Potential space between superficial and deep fascia in males (structures/borders)

- Space ascends abdomen, extends to dorsum of penis into scrotum (in males)

- Laterally ends slightly past inguinal ligament

Superficial fascias in women

Camper and scarpa's fascia extend onto labia majora and perineum

Superficial fascias in men

Scarpa blends:

- Medially with superficial perineal fascia (Colle's fascia) on dorsal penis

- Laterally with darto's fascia of scrotum

Fascial connections in both sexes

Scarpa's — blends with fascia lata of thigh

Camper's — continue into thigh as superficial fascia

Function of abdominal muscles

- Increase abd pressure

- Flex and twist trunk

Flat abdominal muscles

- External oblique

- Internal oblique

- Transversus abdominis

Aponeurosis of flat abdominal muscles

- Start posteriolaterally → transverse anterior to form aponeurosis

- AKA rectus sheath

- Sheath around rectus abdominis muscle

Vertical abdominal muscles

- Near midline, within tendinous sheath

- Rectus abdominis

- Pyramidalis

Most superficial flat muscle

External oblique

Attachments/fibers of external oblique

- Lower 8 ribs (proximal)

- Aponeurosis at linea alba

- Lateral iliac crest and ASIS

- Pubic tubercle

- Fibers "hands in the pocket"

External oblique aponeurosis forms...

- Inguinal ligament

- Floor of inguinal canal

Middle layer of flat muscles

Internal oblique

Attachments/fibers of internal oblique

- Thoracolumbar fascia of back

- Midle iliac crest

- Lateral 2/3 of inguinal ligament

- Aponeurosis at linea alba

- Lower rib border

- Pubic crest

- Fibers "fan" out (superiorly and inferiorly)

Deepest layer of flat muscles

Transverse abdominis

Attachments/fibers of transverse abdominis

- Thoracolumbar fascia of back

- Iliac crest

- Lateral 1/3 of inguinal ligament

- Aponeurosis at linea alba

- Pubic crest

- Fibers transverse

Rectus abdominis (+ fibers)

- Medial (paired) muscle that extends the entire length of abdominal wall

- Vertical fibers

Linea alba

Midline of rectus abdominis

6-pack abdominal appearance is created by...

Tendinous intersections

Linea semilunaris

Lateral boundaries of rectus abdominis

Pyramidalis muscle

- Tenses linea alba

- Connects pubic bone to linea alba

Transversalis fascia

- Bottom layer of deep fascia on transverse abdominis

- Surrounds entire abdominal cavity

- Blends with fascia of inferior diaphragm, enters pelvic cavity

Rectus sheath

- Fibrous sheath formed by aponeuroses of flat abdominal muscles

- Fuses with linea alba at midline

Arcuate line

- Where posterior rectus sheath ends ~1/3 along umbilicus to pubis

- Sheath on top of rectus, transversalis still deep

Peritoneum

Serous - envelopes abd cavity

Parietal - deep to transversalis fascia

Extraperitoneal fascia

Separates parietal peritoneum from the transversalis fascia/body wall (everyone posteriorly, +/- anterior)

(all) Innervation of abdominal wall

- T7 to L1

- Intercostal nerves (T7-T11)

- Subcostal nerve (T12)

- Iliohypogastric and ilioinguinal (L1)

T7-T11 innervation

- Intercostal nerves

- Motor and sensory from xiphoid processes → below umbilicus

T12 innervation

- Subcostal nerve

- Lower external oblique, hip, ASIS

L1 innervation

Iliohypogastric → Lower abdomen skin, iliac crest

Ilioinguinal → Genitals and medial thigh

Level of L1

Pubic area

Level of T10

Umbilicus

Blood supply of abdominal muscles

- Superior epigastric and musculophrenic (from internal thoracic)

- Intercostals

- Inferior epigastric (from external iliac, deep to rectus abdominis)

- Deep circumflex iliac (from external iliac)

Formation of inguinal aponeurosis

- Aponeurosis forms from external oblique, ASIS (laterally), pubic tubercle (medially) → rolls over

- Floor → inguinal ligament

- Shelf → floor for inguinal canal

Structures that form the inguinal ligament

- Floor (inferior) of aponeurosis → inguinal ligament

- Bounded by abdomen and thigh

Inguinal ligament blends with...

- Lateral 1/3 with fascia lata of thigh

- Medial forms superficial inguinal arch

Superficial inguinal arch

Femoral vessels pass under arch to thigh

Inguinal canal

- Shelf of aponeurosis → floor for inguinal canal

- Pathway through anterior abdominal wall

Function of inguinal canal in male development

Pathway for genitalia to become external

Inguinal canal differences between sexes in adults

Males — Spermaticord

Females — Round ligament

Both — Ilioinguinal nerve

Openings of inguinal canal

- Superficial inguinal ring

- Deep inguinal ring

Anterior wall and floor of inguinal canal is formed by...

External oblique aponeurosis

Internal (posterior) wall of inguinal canal is formed by...

- Transversalis fascia

- Conjoint tendon of internal oblique

- Transverse abdominis

Gubernaculum

- Cord that attaches gonad

- Guide gonad to destination (sex differences)

Difference of gubernaculum between sexes

Male — testis → scrotum

Female — Ovary → lateral wall of pelvis

Undifferentiated gonads are formed...

On posterior abdominal wall (retroperitoneal)

Gubernaculum development of males

- Gubernaculum descending into abd wall towards scrotum

- Process vaginalis follows gubernaculum descent & accompanies testis into scrotum → serous sac covering testis (tunica vaginalis)

Process vaginalis

- Pouch of peritoneum

- Begins anterior abd wall, follows gubernaculum

- Origin becomes deep inguinal ring in adult

Tunica vaginalis

- Accompanies testis into scrotum, becomes serous sac covering testis

- Parietal and visceral layers

Spermatic fascia

- All structures that run with testicle through inguinal canal

- Becomes spermatic cord in adults

Cryptorchidism

- Undescended testes

- Testes stay in inguinal canal or external inguinal risk is in high position

Spermatic cord

Encloses nerve fibers, blood vessels, and lymphatics that supply testes

Formation of cremaster muscle

Derived from middle layer of spermatic fascia (internal oblique muscle)

Function of cremaster muscle

Elevates testis for temperature regulation

Cremaster reflex

- Afferents from L1

- Used for detection of testicular torsion or function of SC at L1

Gubernaculum development of females

- Travels to lateral pelvic wall, ovary follows

- Continues to uterus → ovarian ligament

- Through inguinal canal and joins labia majora

- Process vaginalis follows gubernaculum to labia majora

Ovarian ligament

Attaches ovary to uterus

Round ligament of uterus

Through inguinal canal and attaches to the labia majora

Nuck's cyst

- Process vaginalis fails to fuse → patent canal forms to external genitalia forming a fluid filled cyst

Clinical significance of weak point of abdomen

- Inguinal canal (potential for peritoneum to pass)

- Prone to hernias

Indirect hernia

Process vaginalis stays open, peritoneum pushes into scrotum/labia major through deep inguinal ring → inguinal canal

Direct hernia

Inguinal hernia protruding through hesselbach triangle

Inguinal/Hesselbach's triangle

- Near conjoint tendon and lateral to rectus abdominis where abdominal wall is weak

- Location of direct hernia

Abdominopelvic cavity

Abdomen is continuous with pelvic cavity

Borders of abdominal cavity

Superior — diaphragm

Anterolateral — musculoaponeurotic walls

Inferior — pelvic inlet

Pelvic inlet

Line from sacral promotory to superior border of pubic symphysis

Location of parietal peritoneum

Deep to transversalis fascia and extraperitoneal fat

Gut tube/mesentary development

- Abdomen starts with ventral gut tube

- Gut tube sandwiched between peritoneum & attached to posterior wall and anterior wall

Dorsal mesentery

Attaches gut tube to posterior wall

Ventral mesentery

Attaches gut tube to anterior wall

Mesentery

- Middle of intestine

- Double layer peritoneum

Intraperitoneum

Viscera surrounded by peritoneum, suspended from posterior abdominal wall by double layer peritoneum (mesentery)

Retroperitoneum viscera

Viscera only covered by one surface of peritoneum (non-mobile, no mesentery)

Intraperitoneum and retroperitoneum during development

- Structures that start as intraperitoneal can migrate to retroperitoneal (secondarily retroperitoneal)

Ex: Ascending and descending colon

Falciform ligament

- Attaches liver to anterior abdominal wall

- Separates R and L upper abdominal cavity

Round ligament (ligament teres hepatis)

- Within inferior border of falciform ligament

- Remnant of umbilical vein

Lesser omentum

Connects lesser curvature of stomach and upper duodenum with liver

Ligaments of the lesser omentum

Hepatogastic — liver to stomach

Hepatoduodenal — liver to duodenum

Free edge at heptoduodenal ligament triad

- Portal vein

- Proper hepatic artery

- Bileduct

Mesentery (middle of intestine) is attached with...

Small intestine (midgut)

Development of stomach

Rotation to adult position

Greater omentum (+ attachments)

- Varying amounts of fat

- Greater curvature of stomach and 1st part of duodenum

- Attaches to peritoneum on anterior transverse colon

- Blends with peritoneum of posterior wall

Function of greater omentum

- "Abdominal policeman" or "nature's bandaid"

- Adheres to damaged area of viscera

- Provides leukocytes for local immune responses

Attachment of of abdominal visor and posterior wall via.... BUT...

- Mesentery (proper)

- BUT remains mobile

Function of peritoneum/mesenteries

- Frictionless movement of abdominal viscera

- Folds suspend abdominal viscera and act as conduit for nerves and BV to viscera (ex: superior mesenteric artery)

Innervation of peritoneum

Parietal peritoneum — Spinal nerves that innervate dermatomes

Visceral peritoneum — Visceral afferents

Sharp and well-localized pain of peritoneum

Spinal nerves that innervate dermatomes (for parietal peritoneum)

Dull and poorly-localized pain of peritoneum

Visceral afferents (for visceral peritoneum)

Sensory nerves to abdominal wall are the same as...

Parietal peritoneum

Peritonitis & signs/symptoms

- Inflammation of the peritoneum

- Pain, abd distention, fever, decreased urination and defecation

Spontaneous peritonitis

- Infection of peritoneal fluid

- Commonly related to kidney disease (dialysis) or liver disease

Secondary peritonitis

- Result of different infection

- Commonly related to digestive system - burst appendix

MC peritoneal cancer

Secondary peritoneal cancers

Peritoneal cancers

Primary — rare, prognosis highly dependent on stage

Secondary — common

Ascites + cause

- Build up (serous) fluid in peritoneal cavity

- Caused by increased vasculature pressure & low albumin

- Brought on by diseases that cause portal HTN, CHF, renal deficiency/failure

Developing regions of gut tube

- Foregut

- Midgut

- Hindgut